The invention relates to an electrochromic dimming system in accordance with the preamble of the main claim.
Electrochromic dimming systems, e.g. dimming mirrors for motor vehicles are generally known in prior art. An essential element of these electrochromic mirrors is an electrochromic layer arrangement formed from an electrochromic material which, when an electrical field is applied to it, changes its optical constants and thus its visual properties. Typical examples of such electrochromic materials are WO3 and MoO3, which are applied in thin layers to a carrier and are practically colourless. An electrochromic layer can alter its visual properties by oxidation or reduction processes. If protons migrate in such a layer, in the case of tungsten oxide there is a reduction to blue tungsten bronze. The intensity of the colouring is determined by the amount of charge displaced in the layers.
Electrochemical liquids and gels and the like can also be used as the electrochromic material.
To contact the electrodes of such electrochromic systems, which may also serve as display or the like, the carriers bearing the electrodes and consisting of glass for example, are glued slightly offset to one another so that a projecting length remains. By this means, the flat electrodes directed inwards can be provided with contacting. Since the surface resistance of the electrode material is partially very high, the coupling of the electrical current must take place over as large a surface as possible via a good electrical conductor. This is realised with metal clips which are pushed over the projecting edges.
In the described contacting according to prior art, through the offset of the two pieces of glass to one another and the gluing, a broad edge is produced which cannot be darkened or dimmed. In addition, through the coupling of the voltage at the edges via the clips, there exists the problem that leads are supplied at the edge which have to be additionally protected, and this makes greater constructional outlay necessary. As a result of the voltage drop at the electrode which increases with increasing distance from the metal clip, the EC system is darkened non-homogeneously.
The purpose underlying the invention, therefore, is to create an electrochromic dimming system, in which contacting of the electrodes over a large surface is possible whilst minimising the edge necessary as a result of the contacting the position of the electrical connections pins or terminals to the supply should be selectable in a variable way.
This object is achieved according to the invention by the characteristic features of the main claim in conjunction with the features of the preamble.
Because there is arranged on the region of the peripheral edge of a carrier provided with a flat electrode, an annular conductive element which, possibly with the interposition of a conductive layer, is pressed onto the region of the peripheral edge of the second carrier of electrically isolating material receiving the other flat electrode, and because, in the region of the peripheral edge of the second carrier, at least one feedthrough is provided to connect the one electrode with a current/voltage source, contacting of the one electrode of the EC system is possible over a large area. No loss areas arise through crimp contacts and the edge which is not to be darkened can be reduced in a defined manner. Furthermore, contacting which is laid around the edge is avoided. Altogether the structure of the contact arrangement is relatively simple, the connection points may be arranged at any positions or the backside of the second carrier.
Through the measures quoted in the subordinate claims, advantageous developments and improvements are possible.
Particularly advantageous in an application of the electrochromic dimming system for a motor vehicle mirror, [is] the use of a printed circuit board or card since conductor tracks or electronic circuits or electronic components can be attached to the rear side of the printed circuit board. The connection point of the rear electrode can be freely selected and a plurality of feedthroughs which are connected by conductor tracks can be provided. With a multilayer printed circuit board, for example, heating of the mirror can be integrated with corresponding control electronics. A compact unit can be manufactured which is produced from the EC system with control electronics, a mirror heating system and additional electrical elements, such as humidity sensor, display or connector plug. The contacting according to the invention is also suitable for spherical and aspherical mirrors.